444 research outputs found
The effect of growth rate on reproductive outcomes in replacement dairy heifers in seasonally calving, pasture-based systems
peer-reviewedThe effect of average daily gain (ADG) on reproductive outcomes in replacement dairy heifers was investigated. All heifers were managed in the typical Irish spring calving, pasture-based system, where the herd calves in 1 block between January and April and the majority of the diet comprises grazed grass. Heifer calves (n = 399) from 7 herds were weighed at birth and at the beginning of the breeding season, and ADG was calculated. Service dates and pregnancy diagnosis results were recorded, and conception dates were calculated. Days open (DO) was defined as the number of days between the beginning of the breeding season and conception. Genetic data were retrieved from the Irish Cattle Breeding Federation database. A Cox proportional hazard model was constructed to identify variables with a significant effect on DO. An accelerated failure time model was used to predict survival curves and median survival times for different combinations of the significant variables. The ADG ranged from 0.41 to 0.91 kg/d, with a median of 0.70 kg/d. Frailty effect of farm within year, maintenance subindex of the economic breeding index, and ADG had a significant effect on DO. Derived from the final accelerated failure time model, the predicted median DO for a heifer with an ADG of 0.40, 0.70, or 0.90 kg/d aged 443 d at the beginning of the breeding season and with a maintenance subindex in the second tercile were 27, 16, and 11 d, respectively
The effect of dairy heifer pre-breeding growth rate on first lactation milk yield in spring-calving, pasture-based herds
peer-reviewedOptimising heifer growth rate may offer an opportunity to improve lifetime milk yield per cow, enhancing the environmental and economic efficiency of dairy farming operations. The effect of dairy heifer pre-breeding average daily weight gain (ADGPB) on first lactation milk yield was investigated. This observational study employed a data set comprising 265 Holstein-Friesian, or Holstein-Friesian-cross-Jersey heifers from seven commercial, spring-calving, pasture-based dairy herds, where the major component of the diet was grazed grass. These were weighed at birth and prior to breeding and ADGPB was calculated. Milk recordings were performed throughout the heifers' first lactation and 305-day yield figures calculated from these records. Yields were corrected to 4% fat and 3.1% protein to create standardised 305-day milk yield (SMY), which was the outcome of interest. Median ADGPB was 0.72 kg/day. Median 305-day yield was 5 967 kg. Linear regression was used to investigate the effect of weight and genetic, age and first calving factors on SMY. Pre-breeding average daily weight gain, age at first calving and predicted transmitting abilities for milk protein production and calving interval were all significant in the final model, which also included the random effects of farm and month of calving within year. ADGPB was quadratically related to first lactation SMY, with an ADGPB of 0.82 kg/day corresponding to the maximum predicted SMY. The model predicted that a heifer growing at 0.82 kg/day would produce 1 120 kg more SMY than a heifer growing at 0.55 kg/day, 218 kg more than a heifer growing at 0.7 kg/day and 103 kg more than a heifer growing at 0.90 kg/day. Manipulation of heifer growth rate may offer a viable method of increasing first lactation milk yield
Young pregnant women and risk for mental disorders: findings from an early pregnancy cohort
BACKGROUND:Young women aged 16-24 are at high risk of common mental disorders (CMDs), but the risk during pregnancy is unclear.AimsTo compare the population prevalence of CMDs in pregnant women aged 16-24 with pregnant women ≥25 years in a representative cohort, hypothesising that younger women are at higher risk of CMDs (depression, anxiety disorders, post-traumatic stress disorder, obsessive-compulsive disorder), and that this is associated with low social support, higher rates of lifetime abuse and unemployment. METHOD:Analysis of cross-sectional baseline data from a cohort of 545 women (of whom 57 were aged 16-24 years), attending a South London maternity service, with recruitment stratified by endorsement of questions on low mood, interviewed with the Structured Clinical Interview DSM-IV-TR. RESULTS:Population prevalence estimates of CMDs were 45.1% (95% CI 23.5-68.7) in young women and 15.5% (95% CI 12.0-19.8) in women ≥25, and for 'any mental disorder' 67.2% (95% CI 41.7-85.4) and 21.2% (95% CI 17.0-26.1), respectively. Young women had greater odds of having a CMD (adjusted odds ratio (aOR) = 5.8, 95% CI 1.8-18.6) and CMDs were associated with living alone (aOR = 3.0, 95% CI 1.1-8.0) and abuse (aOR = 1.5, 95% CI 0.8-2.8). CONCLUSIONS:Pregnant women between 16 and 24 years are at very high risk of mental disorders; services need to target resources for pregnant women under 25, including those in their early 20s. Interventions enhancing social networks, addressing abuse and providing adequate mental health treatment may minimise adverse outcomes for young women and their children.Declaration of interestNone
Measuring student teachers' basic psychological needs
In the Self-Determination Theory (SDT) basic psychological needs for relatedness, autonomy and competence are distinguished. Basic psychological need fulfilment is considered to be critical for human development and intrinsic motivation. In the Netherlands, the concept of basic psychological need fulfilment is introduced in the curricula of many teacher education institutes. In five teacher education institutes for primary school teachers, study coaches use a Dutch version of the Basic Psychological Needs Scale (BPNS), to collect data to be used in a discussion with student teachers about their intrinsic motivation for a specific part of the teacher education course. On the basis of the outcomes of this discussion, study coaches and student teachers derive consequences for day to day practice in their classrooms. The data were also used to establish whether the theoretical distinction between three basic psychological needs is found in this sample of student teachers in the Netherlands.
The results show that the constructs of relatedness, autonomy and competence are found and can be measured by using a 14-item five-point scale, partly based on the original BPNS, and partly on new items that focus on different sources of perceived need fulfilment, namely teacher education in general, the study coach and fellow students
Higher spin quaternion waves in the Klein-Gordon theory
Electromagnetic interactions are discussed in the context of the Klein-Gordon
fermion equation. The Mott scattering amplitude is derived in leading order
perturbation theory and the result of the Dirac theory is reproduced except for
an overall factor of sixteen. The discrepancy is not resolved as the study
points into another direction. The vertex structures involved in the scattering
calculations indicate the relevance of a modified Klein-Gordon equation, which
takes into account the number of polarization states of the considered quantum
field. In this equation the d'Alembertian is acting on quaternion-like plane
waves, which can be generalized to representations of arbitrary spin. The
method provides the same relation between mass and spin that has been found
previously by Majorana, Gelfand, and Yaglom in infinite spin theories
Search for lepton-flavor violation at HERA
A search for lepton-flavor-violating interactions and has been performed with the ZEUS detector using the entire HERA I
data sample, corresponding to an integrated luminosity of 130 pb^{-1}. The data
were taken at center-of-mass energies, , of 300 and 318 GeV. No
evidence of lepton-flavor violation was found, and constraints were derived on
leptoquarks (LQs) that could mediate such interactions. For LQ masses below
, limits were set on , where
is the coupling of the LQ to an electron and a
first-generation quark , and is the branching ratio of
the LQ to the final-state lepton ( or ) and a quark . For
LQ masses much larger than , limits were set on the four-fermion
interaction term for LQs that couple to an electron and a quark
and to a lepton and a quark , where and are
quark generation indices. Some of the limits are also applicable to
lepton-flavor-violating processes mediated by squarks in -Parity-violating
supersymmetric models. In some cases, especially when a higher-generation quark
is involved and for the process , the ZEUS limits are the most
stringent to date.Comment: 37 pages, 10 figures, Accepted by EPJC. References and 1 figure (Fig.
6) adde
Multijet production in neutral current deep inelastic scattering at HERA and determination of alpha_s
Multijet production rates in neutral current deep inelastic scattering have
been measured in the range of exchanged boson virtualities 10 < Q2 < 5000 GeV2.
The data were taken at the ep collider HERA with centre-of-mass energy sqrt(s)
= 318 GeV using the ZEUS detector and correspond to an integrated luminosity of
82.2 pb-1. Jets were identified in the Breit frame using the k_T cluster
algorithm in the longitudinally invariant inclusive mode. Measurements of
differential dijet and trijet cross sections are presented as functions of jet
transverse energy E_{T,B}{jet}, pseudorapidity eta_{LAB}{jet} and Q2 with
E_{T,B}{jet} > 5 GeV and -1 < eta_{LAB}{jet} < 2.5. Next-to-leading-order QCD
calculations describe the data well. The value of the strong coupling constant
alpha_s(M_Z), determined from the ratio of the trijet to dijet cross sections,
is alpha_s(M_Z) = 0.1179 pm 0.0013(stat.) {+0.0028}_{-0.0046}(exp.)
{+0.0064}_{-0.0046}(th.)Comment: 22 pages, 5 figure
Measurement of (anti)deuteron and (anti)proton production in DIS at HERA
The first observation of (anti)deuterons in deep inelastic scattering at HERA
has been made with the ZEUS detector at a centre-of-mass energy of 300--318 GeV
using an integrated luminosity of 120 pb-1. The measurement was performed in
the central rapidity region for transverse momentum per unit of mass in the
range 0.3<p_T/M<0.7. The particle rates have been extracted and interpreted in
terms of the coalescence model. The (anti)deuteron production yield is smaller
than the (anti)proton yield by approximately three orders of magnitude,
consistent with the world measurements.Comment: 26 pages, 9 figures, 5 tables, submitted to Nucl. Phys.
Measurement of beauty production in deep inelastic scattering at HERA
The beauty production cross section for deep inelastic scattering events with
at least one hard jet in the Breit frame together with a muon has been
measured, for photon virtualities Q^2 > 2 GeV^2, with the ZEUS detector at HERA
using integrated luminosity of 72 pb^-1. The total visible cross section is
sigma_b-bbar (ep -> e jet mu X) = 40.9 +- 5.7 (stat.) +6.0 -4.4 (syst.) pb. The
next-to-leading order QCD prediction lies about 2.5 standard deviations below
the data. The differential cross sections are in general consistent with the
NLO QCD predictions; however at low values of Q^2, Bjorken x, and muon
transverse momentum, and high values of jet transverse energy and muon
pseudorapidity, the prediction is about two standard deviations below the data.Comment: 18 pages, 4 figure
Measurement of charm fragmentation ratios and fractions in photoproduction at HERA
The production of D^*+, D^0, D^+, D_s^+ and Lambda_c^+ charm hadrons and
their antiparticles in ep scattering at HERA was measured with the ZEUS
detector using an integrated luminosity of 79 pb^-1. The measurement has been
performed in the photoproduction regime with the exchanged-photon virtuality
Q^2 < 1 GeV^2 and for photon-proton centre-of-mass energies in the range 130 <
W < 300 GeV. The charm hadrons were reconstructed in the range of transverse
momentum p_T(D, Lambda_c) > 3.8 GeV and pseudorapidity |eta(D, Lambda_c)| <
1.6. The production cross sections were used to determine the ratio of neutral
and charged D-meson production rates, R_u/d, the strangeness-suppression
factor, gamma_s, and the fraction of charged D mesons produced in a vector
state, P_v^d. The measured R_u/d and gamma_s values agree with those obtained
in deep inelastic scattering and in e^+e^- annihilations. The measured P_v^d
value is smaller than, but consistent with, the previous measurements. The
fractions of c quarks hadronising as a particular charm hadron, f(c -> D,
Lambda_c), were derived in the given kinematic range. The measured open-charm
fragmentation fractions are consistent with previous results, although the
measured f(c -> D^*+) is smaller and f(c -> Lambda_c^+) is larger than those
obtained in e^+e^- annihilations. These results generally support the
hypothesis that fragmentation proceeds independently of the hard sub-process.Comment: 29 pages, 5 figures, 6 tables; minor text revision
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